The invention relates to an apparatus for the compacting of granular molding materials and, more particularly, foundry molding materials.
Swiss Patent Specification No. 660,987 discloses an apparatus for compacting molding material wherein the molding means filled with molding material is transported on a lifting table which raises the molding means against an adaptor plate of a pressure chamber arranged on supports.
In the connection of granular foundry molding materials, a certain pressure level over the foundry material is necessary for the compacting operation in order to insure that the molding material is accelerated in the direction of the pattern or pattern plate carrier and its support. This pressure level P1 is applied by using a surge of compressed air, gas-explosion pressure or the like. After this first pressure level is withdrawn, a second reaction pressure P2 of about twice the level of the first pressure level P1 necessary for the acceleration is applied for further compacting the molding material, that is, P2.perspectiveto.2P1.
In the case of the apparatus according to Swiss Patent Specification No. 660,987, the contact force of the lifting table must correspond at least to the force of the second reaction pressure P2 in order to press the molding means against the compression or compacting means. A disadvantage in this arrangement is that the lifting table, the hydraulics and the machine rack have to be designed for these high forces. As a result, the apparatus has to be of a heavy duty and expensive design.
Accordingly, it is an object of the present invention to provide an apparatus for compacting granular molding material which overcomes the aforementioned disadvantages.